Electronically controlled electromagnetic pump system



Jan. 2, 1968 E. D. LONG 3,361,069

ELECT RONICALLY CONTROLLED ELECTROMAGNETIC PUMP SYSTEM Filed March 7,1966 3 Sheets-Sheet 1 WITNESS: BY 060? I ATTORNEY Jan. 2, 1968 Y E. D.LONG 3,361,059

ELECTRONICALLY CONTROLLED ELECTRCMAGNETIC PUMP SYSTEM Filed March 7,1966 3 Sheets-Sheet 2 INYENTOR.

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ATTORNEY Jan. 2, 1968 E. D. LONG 3,361,069

ELECTRONICALLY CONTROLLED ELECTROMAGNETIC PUMP SYSTEM 5 Sheets-Sheet 3Filed March 7, 1966 INVENTOR.

WITNESS.

United States Patent ABSTRACT OF THE DISCLOSURE A reciprocatingelectromagnetic pump having a solenoid to move a piston to the inlet endof the cylinder and a spring urging the piston toward the other end ofthe cylinder. The solenoid is periodically energized by a magnetic fieldcausing a flux across the outlet end of the cylinder to operate amagnetically actuated switch.

The present invention relates to an electronically controlledelectromagnetic pump system, and more particularly a system of the typeemploying a pump having an electromagnetically operated reciprocatingpiston for supplying fluid under pressure.

It is an object of the present invention to provide a novel pump systemof the above type which is ellicient and reliable in operation over longperiods of use, which is simple and economical in construction, andwhich op crates consistently irrespective of the attitude of itsmounting, and/ or subjection to severe vibration.

Further objects and advantages will be apparent from the followingdescription, taken in connection with the accompanying drawing, inwhich:

FIGURE 1 is vertical sectional view of a preferred embodiment of theinvention, taken on the line 1-1 of FIG- URE 2,

FIGURE 2 is a top plan view of the structure shown in FIGURE 1, with thetop cover removed, and before the insertion of the potting compound,

FIGURE 3 is a wiring diagram of the pump system, and

FIGURE 4 is a graph illustrating the characteristics of applicant'simproved form of pump spring as compared to a conventional spring.

In FIGURE 1 there is illustrated a casing 1 comprising an inlet chamber2, a pump chamber 3 and an outlet chamber 4. The inlet chamber containsa filter 5, and a check valve 6 which is mounted in a sleeve 7 extendingdownward from a partition 8 which separates the pump chamber 3 from theinlet chamber.

A cylinder 9 of non-magnetic material is axially mounted in the pumpchamber 3 in position to connect the inlet chamber 2 to the outletchamber 4, and a hollow piston 11 of magnetic material, slidably mountedin said cylinder has a second check valve 12 so located therein thatreciprocation of the piston causes fluid to flow through the cylinder 9from the inlet to the outlet chamber. Electromagnetic means foractuating the piston 11 is provided comprising a solenoid 13 located inthe pump chamber surrounding the cylinder and piston, having circularpole pieces 14 and 15 connected by a cylindrical housing 16 of magneticmaterial. A spring 17 urges the piston 11 upwardly to a decenteredposition with respect to the solenoid, and energization of the solenoiddraws the piston down, cooking the spring. When the solenoid isdeenergized, the spring expands and moves the piston through itsdischarge stroke.

Means are provided for periodically energizing the solenoid to causereciprocation of the piston. As best shown in FIGURES 3 and 2, thismeans comprises a source of electrical energy 18, the negative pole ofwhich is "ice grounded, and the positive pole connected through a manualswitch 20 to the emitter of a PNP type transistor 19. The collector ofsaid transistor is connected to one terminal of the solenoid 13, theother terminal of which is grounded to complete the circuit so that whenthe transistor is rendered conductive, the solenoid is energized bysubstantially the voltage of the power source 18.

In order to render the transistor 19 so conductive, the base of thetransistor is connected to the ground, and thus to the negative terminalof the power source, through a current-limiting noninductive resistor21. The value of this resistor is so selected that the base currentthere through heavily saturates the collector-emitter junction of thetransistor and makes the transistor freely conductive in the solenoidcircuit.

In order to periodically render the transistor non-conductive,deenergizing the solenoid 13 and permitting the spring 17 to effect thedischarge stroke of the piston 11, the base and emitter of thetransistor are connected through a switch 22, the operation of which iscontrolled by the movement of the piston 11.

The switch 22 is of the type known as a reed switch, and comprises apair of conductors in the form of blades or reeds of elastic magneticmaterial having cantilever mounts in the ends of a sealed cylindricalcapsule, the free ends of the reeds overlapping and normally spacedslightly out of contact. When the switch is placed in a magnetic fieldwith its axis parallel to the path of fiux, the overlapping ends of themagntic conductors are drawn into contact and the switch is thus closed.

As shown in FIGURE 2, the switch 22 is mounted in a cradle-frame 23 ofnon-magnetic material in a position substantially tangent to the pumpcylinder 9, adjacent to the upper end of the piston 11 when the pistonis at the end of its discharge stroke as defined by the elasticabutments 24, 25 (FIGURE 1) formed on the frame 23. Permanent barmagnets 26 and 27 are mounted in alignment in the frame 23 insubstantially the same horizontal plane as the switch 22, on oppositesides of the pump cylinder 9, with unlike poles facing each other andslightly overlapping but spaced from the ends of said switch. By thisarrangement, the switch 22 is embraced in the field created by themagnets 26, 27 and is closed by the flux in said field when the piston11 has been drawn away by the solenoid 13. When the piston is at theupper end of its stroke, however, the piston forms a path of lowreluctance for the magnetic flux, bypassing the switch 22 and allowingit to open.

In order to permanently and rigidly anchor all the fixed components inthe pump chamber and the outlet chamber, after assembly of the parts,these chambers are evacuated and then filled with a suitable pottingcompound such as an epoxy resin in liquid state to the level of theupper end of the pump cylinder 9. This cylinder may, of course, beformed of a non-magnetic metal such as brass. However, it is in thepurview of the invention to form the cylinder itself of the pottingcompound as shown in FIGURE 1. For this purpose, a cylindrical mandrelhaving the diameter of the piston plus normal clearance is insertedprior to the potting operation, and withdrawn after the resin has cured.The resin forming the cylinder may be impregnated with material toreduce friction and improve its physical properties.

Another feature of the present invention relates to specialcharacteristics of the pump spring 17.

An ordinary coiled compression spring has a force-displacement graphwhich is substantially a straight line throughout its normal operatingrange. In FIGURE 4, which shows force plotted against piston travel, thecurve A shows such a graph of a pump employing a conventional coiledspring. It will be seen that starting with an initial compressive forceof F when the piston reaches the end of its downward stroke, the springexerts a pressure of F to initiate the discharge stroke of the piston.The curve B represents the force exerted on the piston by the solenoidto cock the spring. It will be seen that this force increases as thepiston is drawn into the solenoid from an initial force of F to a valueof F as the piston approaches the end of its downward stroke. Theexcessive force represented by F minus F merely accelerates the pistonabove its most efiicient speed, the energy being wasted in turbulenceand wire-drawing of the liquid through the check valve 12.

Applicant utilizes a substantial portion of this wasted energy byemploying a variable-rate spring designed to have a force-displacementcurve conforming approximately to the curve B, whereby more of theenergy provided by the solenoid is stored up in the spring and madeavailable for moving the piston through its discharge stroke. Thus,starting from the initial compression F the force increases to the valueF the vertical distance between corresponding points on curves B and Cremaining on the order of that between F and F which represents theoptimum force differential for actuation of the piston. Springs havingthe desired characteristics may be of volute or truncated conicalcontour, or may, as illustrated in FlGURE l, have a gradually increasingpitch so that the convolutions of low pitch progressively come intocontact.

In operation, closure of the manual switch 20 connects the positiveterminal of the power source to the emitter of the transistor 19. Sinceat this time the reed switch 22 is open, the current flow through theresistor 21 saturates the collector-emitter junction of the transistor,rendering it conductive and thus causing energization of the solenoid13. When the solenoid has drawn the piston 11 down out of the vicinityof the magnets 26, 27, the flux between the magnets becomes effective toclose the magnetic switch 22. The base current provided by resistor 21is thus by-passed around the base-emitter junction of the transistor,whereby the flow of current through the solenoid 13 is interrupted. Thespring 17 then expands, actuating the piston 11 through its dischargestroke until its upper end enters the field of the magnets 26, 27. Theflux through the magnetic reed switch is thereby bypassed through thepiston, the switch opens, and the operation is repeated. Since thecircuit of the reed switch is non-inductive and of small value, littleor not sparking occurs at the contacts, and the useful life of theswitch is practically unlimited.

It will be understood that the expressions up, down, vertical, andhorizontal are here used merely for convenience in referring to thedrawing. Actually the pump is completely indifierent to orientation andworks equally well in all positions.

The above-described circuit connections are particularly advantageoussince the transistor is thereby permitted to operate under BVCsconditions with the inductive collector load. In other words, when thecurrent through the solenoid is interrupted, the surge of counter EMFcaused by the collapse of the field around the solenoid finds thetransistor with its base shorted to the emitter through the reed switch22. Under this condition the break-down voltage from the collector tothe emitter is so high as to preclude any malfunction. Obviously thisarrangement avoids any problem of sparking or radio interference, andtakes advantage of the almost unlimited service life of the transistor.

Although certain structure has been shown and described in detail, itwill be understood that other embodiments are possible, and changes maybe made in the design and arrangement of the parts without departingfrom the spirit of the invention.

I claim:

1. A pump system comprising a casing having an inlet chamber and anoutlet chamber,

a cylinder of non-magnetic material connecting said chambers,

a hollow piston of magnetizable material slidably mounted in saidcylinder,

a spring urging the piston toward the outlet end of the cylinder,

a solenoid surrounding the cylinder and piston and adapted, whenenergized, to draw the piston toward the inlet end of the cylinder,

valve means in cooperation with the solenoid for causing reciprocationof the piston to produce a flow of liquid from the inlet chamber throughthe piston into the outlet chamber,

and means for periodically energizing said solenoid comprising meansproviding a magnetic field causing a flux across the outlet end of thecylinder,

a magnetically actuated switch located adjacent the outlet end of thecylinder in position to be actuated by said magnetic field,

and means controlled by said switch for causing deenergization of thesolenoid when the piston approaches the inlet end of the cylinder, andmeans forming a conductor for the fiux of said magnetic field by thepiston when the piston moves to the outlet end of the cylinder whereinsaid flux by-passes said switch to allow it to open.

2. A pump as set forth in claim 1 in which the lastmentioned meansincludes a source of electrical energy,

a transister in circuit with said source and the pump solenoid arranged,when rendered conductive, to cause energization of the solenoid,

and circuit connections from said switch to the transtor and the sourceof power whereby when the magnetic flux is by-passed from the switch bythe piston, the switch operates to render the transistor conductive.

3. A pump system as set forth in claim 1 including further,

means filling the space in the housing between the inlet and outletchambers, locating and immobilizing the cylinder, the solenoid, and thecontained elements of the means for energizing the solenoid.

4. A pump system as set forth in claim 3 in which said cylinder isformed of material similar to said filling means, and its integraltherewith.

5. A pump system as set forth in claim 1 in which the means providingthe magnetic field comprises poles of opposite polarity located adjacentopposite sides of the cylinder,

and the magnetically actuated switch comprises parallel overlappingmagnetic contact blades located within said magnetic field and extendingparallel to the direction of flux between said magnetic poles.

6. A pump system as set forth in claim 5 in which the contact blades ofthe switch are so mounted as to be normally out of engagement, but theoverlapping portions are magnetically held together by flux from themagnetic field as long as said flux is not by-passed therefrom by thepresence of the piston in the space between said poles.

7. A pump system as set forth in claim 2 in which the circuitconnections of said transistor and switch comprise means for supplying acurrent through the base-emitter junction of the transistor sufiicientto heavily saturate the collector-emitter junction and thus render thetransistor conductive for current through the solenoid,

said switch being so connected that, when closed, it

by-passes said base-emitter junction of the transistor, stopping theflow of current therethrough and hence rendering the transistornon-conductive for solenoid current.

8. A pump system as set forth in claim 1 in which the means forenergizing the solenoid includes a direct-current source of electricalenergy,

a transistor,

a conductive connecting one terminal of the source of energy to theemitter of the transistor,

a conductor connecting the collector of the transmitter to one terminalof the solenoid,

a conductor connecting the other terminal of the solenoid to the otherterminal of the source of energy,

means including a current-limiting resistor connecting the base of thetransistor to said other terminal of the source of energy,

and means forming a connection through said magnetically operated switchfrom said one terminal of the source of energy to said base of thetransistor.

9. A pump system as set forth in claim 1 in which the means forenergizing the solenoid includes a direct-current source of electricalenergy,

a PNP type transistor having its emitter connected to the positiveterminal of the source of energy, and its collector connected throughsaid solenoid to the negative terminal of said source of energy,

means including a current-limiting resistor connecting the base of thetransistor to said negative terminal of the source of energy,

and a shunt circuit including said magnetically operated switch,connecting the base of said transistor to its emitter.

10. An electronically controlled electro-magnetic pump system as setforth in claim 1 in which said spring which urges the piston toward theoutlet end of the cylinder is so formed that its compressive forceincreases at a higher rate than a linear function of the compressionstroke.

11. A pump system as set forth in claim 10 in which said spring has aforce-displacement curve the contour of which approximates that of theactuation of the piston by the solenoid.

References Cited UNITED STATES PATENTS 2,666,153 1/1954 McHenry et al10353 X 3,000,321 9/1961 Parker 103-53 3,113,523 12/1963 Woodward et a1.10353 ROBERT M. WALKER, Primary Examiner.

